Sort and Paginate articles by # number of comments

Rails
1

hello list,

i am programming a function to sort articles by the number of comments
they
had today but i keep having sql errors
i want to use something like (doesnt work actually)

@articles = Articles.find(:all, :include => ‘comments’, :conditions =>
[’
comments.created_at >', Time.now - 86400], :order => 'COUNT(comments.id)
')

it is in :order i dont really know what to put in

i can do it in about 2 lines without the :order and then with a sort!
but i
want now to paginate so i need to wrap it all in 1 sql query.
??

thanks

–
Heri R.
http://sprinj.com

2

This one was a brainbuster. Seriously. I’m lucky it’s the end of the
work day because I’m done.
This is a beast of a query, and with the 200,000 row child table I
tested it on, it took a while.

select *
from articles
inner join comments on articles.id = comments.article_id
group by articles.id
order by count(*) DESC;

BAM.

3

Jason N. wrote:

This one was a brainbuster. Seriously. I’m lucky it’s the end of the
work day because I’m done.
This is a beast of a query, and with the 200,000 row child table I
tested it on, it took a while.

select *
from articles
inner join comments on articles.id = comments.article_id
group by articles.id
order by count(*) DESC;

BAM.

I’m sure the biggest bottleneck here is the 200,000 record resultset.
ActiveRecord will choke on this large of a resultset. The query itself
probably runs pretty fast. I actually had to give up on using
ActiveRecord (and eventually Ruby altogether) for a project because of
this. I bet if you include a LIMIT/OFFSET (pagination) in there it’ll
run a lot faster.

-matthew

4

thanks jason, but doesnt seem to work, i get a “#HY000 Invalid use of
group
function” error

Article.find_by_sql(select articles.*, count(comments.id)
inner join comments on articles.id = comments.article_id
group by articles.id WHERE comments.created_at >
…yesterdaysDate…
order by 2 DESC)

works though (instead of order by count(*)

–
Heri R.
http://sprinj.com